Cold-box resin-bonded foundry core-making machine

ABSTRACT

An apparatus for performing the method of producing resin-bonded foundry cores by the cold-box technique which involves delivering two segregated mixes, of sand and resin and of sand and hardener respectively, into a mixing device to produce a homogeneous final mixture of all the materials, and blowing the final mixture into a mould cavity in a corebox.

United States Patent [72] Inventors Derek Randolph Bayliss [50] FieldofSearch...... 164/l9- Kidderrninster; -22, l92-l94, 198-202 Terence Hugh Middleton, Shirley, both of, Enghmd References Cited UNITED STATES PATENTS [2|] AppLNo.

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[54] COLIHKX RESlN B0NDED FOUNDRY CORE ABSTRACT: An apparatus for performing the method of producing resin-bonded foundry cores by the cold-box MAKING MACHINE technique which involves delivering two segregated mixes, of

3 Claims, 5 Drawing Figs.

PATENTED JUL 6 15m SHEET 1 BF 5 PATENTEB JUL 6197] SHEET 2 BF 5 PATENTED JUL 6 l97l SHEET 3 OF 5 PATENTEU JUL BIG?! 3 590 906 saw u or s Inventor Attorney PATENTEU JUL 6 |97| SHEET 5 BF 5 COLD-BOX RESIN-BONDED FOUNDRY CORE-MAKING MACHINE This invention relates to the manufacture of foundry cores on a flow-production basis.

The general foundry practice for manufacturing accurate and repetitively consistent cores is, basically, to use phenolic or other thermosetting resins which, in the presence of an acid catalyst, are mixed in the correct proportions with the particular grade or grades of sand which may be required. There is little or no reaction between the resin and the catalyst (within the time required to mix them thoroughly) until heat is applied to the mix, the resin then becoming cross-linked and setting into a consolidated shape.

In order to be able to employ that procedure in production, it is necessary to have metal coreboxes of which the sections are sufficiently massive to withstand the distortion which would otherwise be caused by the high temperatures needed to bring about cross-linking of the resin; and also to act as a heat sump, to prevent the sand-and-resin mix extracting an ex cessive amount of heat from its immediate vicinity. The corebox temperatures are usually in excess of 200 C., and the machinery involved in handling these coreboxes has to be of quite robust design in order to carry the weight involved. This machinery is extremely expensive and utilizes large amounts of power, resulting in high-power costs.

Another method of making resin-bonded foundry cores employs the so-called cold-box. In this case the heat needed to effect cross-linking of the resin is not applied externally, but is derived from the exothermic chemical reaction that takes place between the resin and a hardener. As the temperature reached in the reaction is comparatively low, the coreboxes can be manufactured from materials which only have to withstand the following:

I. The clamping stresses required to keep the box shut.

2. The wear and tear caused when the sand-and-resin mix is blown into the box.

3. The blowing pressure when the airblast is operating.

It is also necessary to ensure that dimensional tolerances are maintained at all times.

The cold-box technique enables the thickness of the sections of a corebox to be reduced by over 50 percent as compared with what obtains in the case of a system that requires the application of external heating; and, in addition, the materials used in the manufacture of the coreboxes are much cheaper, owing to the absence of thermal cycling and distortion due to thermal gradients within the box.

As the chemical reaction between the resin and the hardener commences immediately they are brought together, it has been found that the time available for mixing the sand, resin and hardener and dispensing the mix into the corebox is a maximum of approximately 35 seconds. Consequently, owing to the risk of machinery breaking down or power cuts occurring during production, it is not practicable to effect continuous mixing of the materials (such that they are drawn off at the required rate) because the chemical reaction, initiated by the mixing, cannot be prevented from going past the point of no return. The implication is that, should there be either a mechanical breakdown or a power cut, the whole system would be filled with reacting material which would harden and therefore have to be removed (entailing great difficulty) before the system could be restarted.

The object of the present invention is to enable resinbonded foundry cores to be manufactured on a flow-production basis, without incurring any of the disadvantages or problems associated with the procedures already described. To this end, according to the invention, a method of producing such cores by employing the cold-box technique comprises mixing (in the requisite proportions) controlled amounts of sand and resin on the one hand, and of sand and hardener on the other hand; delivering the two segregated mixes into a mixing device to produce a homogeneousfinal mixture of all the materials; dispensing the final mixture into a blowing chamber; obturating communication between the mixing device and the blowing chamber, and then applying an airblast to that chamber to blow the final mixture into a mold cavity in a corebox.

By this invention the core-making process, although it is continuous, is constituted by a sequence of discrete phases of operation, and the requisite quantities of the core-making materials are accurately metered so that, at each stage, there is no excess material in the system. Moreover, each of the operating phases is arranged to be interlocked with the others by time controlled mechanism.

A core-making machine designed to operate in accordance with the invention comprises, in combination, a hopper containing sand of which the temperature and moisture content are controlled (to ensure substantially constant, and therefore repetitively consistent, operating conditions), the sand hopper having two timer-controlled outlet valves; two separate mixing devices to which controlled amounts of sand are delivered form the respective hopper outlets; means for supplying resin to one of the mixing devices; means for supplying hardener to the other mixing device; two separate hoppers into which the segregated mixes are delivered; a final mixer for producing a homogeneous mixture of all the materials; timer-controlled outlet valve means by which the respective mixes are delivered to the final mixer; a blowing chamber serving a cold corebox; timer-controlled valve means for dispensing the final mix into the blowing chamber; and a timer-controlled valve effective to obturate communication between the final mixer and the blowing chamber before the final mixture is blown into the corebox.

A core-making machine designed to operate in accordance with the invention will now be described, by way of illustration, with reference to the accompanying drawings in which:

FIG. 1 shows a schematic view of the machine in isometric projection;

FIG. 2 is a perspective view of an assembly, comprising a pair of hoppers and associated slide valve means, which forms part of the machine shown in FIG. 1;

FIG. 3 is a perspective view showing how the final mixer of the machine is mounted;

FIG. 4 is a broken perspective view showing a slide-valve that controls the outlet ofthe final mixer; and

FIG. 5 is a fragmentary perspective view showing a slidevalve that controls communication between the final mixer and a blowing chamber.

A hopper 1 (FIG. 1) contains sand of which the temperature and moisture content and controlled (to ensures substantially constant, and therefore repetitively consistent, operating conditions). The base of the sand hopper l is fitted with two timer-controlled outlet valves 2 of the slidable-plate type, each valve controlling its own discharge outlet 3 which, conveniently, may be a circular hole in the base of the hopper. The controlling edge of each slidable valve 2 incorporates a V shaped notch 4 which affords a variable area aperture as it is moved across the corresponding outlet 3. In this way the rate of discharge of the sand can be regulated in dependence upon the size of the particular core which is to be mode at any time.

Two mixing devices 5 and 6 of the continuous screw type are disposed side by side, with their respective inlets 7 in registration with the discharge outlets 3 of the sand hopper l. Resin from a tank 8 is delivered by a pump 9 an pipe 10 to the mixing device 5; and hardener from a tank 11 is delivered by a pump 12 and pipe 13 to the mixing device 6. In consequence, two segregated mixes are produced; namely, resin/ sand and hardener/sand respectively. The resin tank 8 and the hardener tank 11 have their temperature and moisture content controlled, to ensure substantially constant metering. Also, the resin pump 9 and the hardener pump 12 are of variable output; so that exact metering to suit any volume of sand can be achieved.

The mixing devices 5 and 6, each of which has its own driving shaft 14, deliver the segregated mixes through spouts l5 and 16 into separate hoppers 17 and 18. Each of these hoppers has a bottom outlet controlled by a timer-controlled valve 19, of the slidable plate type, which works in guides 20 and 20A; the guides 20 being fixed to the respective halves ofa girderlike support frame 21, which is mounted on pillars 22. The hoppers 17 and 18 (see HO. 2) are each supported by an attached strap 23 bolted to the corresponding guide 20; and the central guide 20A is bolted to a pair of angle brackets 24 attached to each of the hoppers 17 and 18. The respective slidevalves 19 are rigidly interconnected by a transverse bar 25 which is secured to a piston rod 26 of a pneumatic cylinder (not shown).

A final mixer 27 of the paddle type, having a driving shaft 28 supported by the guide 20A and accommodated in a gap between the hoppers l7 and 18, is mounted so that it lies beneath these hoppers in position to receive their discharges when the intervening control valve 19 is opened. The final mixer 27 is accommodated in a gap between the two halves of the frame 21 and, as shown in FIG. 3, is mounted by four brackets 29 secured to the frame 21. As paddle-type mixers are well known, it has not been deemed necessary to illustrate the actual stirring paddles mounted on the driving shaft 28.

The final mixer 27 is supported so that its open bottom lies immediately above a timer-controlled slide-valve 30 (FIG. 4) which, for the sake of clarity in the drawing, has not been shown in FIG. 1. The slide-valve 30 works in guides 31 fixed to a girderlike support frame 32 mounted on the pillars 22. it has an aperture 33, through which the contents of the final mixer 27 can be discharged, and (like the valve 19) is operated pneumatically. The webs of the girderlike frame 32 each have a V-shaped notch 34, in order to cradle a conical funnel 35 beneath the slide-valve 30.

There is a further timer-controlled slide-valve 36 (FIG. 5), which has not been shown in the schematic view (FIG. ll). It works in guides 37 fixed to the underside of the girderlike support frame 32, and is operated by a piston rod 38 of a pneumatic cylinder (not shown). The valve 36, which has an aperture 3? that can be brought into registration with the outlet of the conical funnel 35, serves to obturate communication between the final mixer 27 and a blowing chamber 40 (FIG. 1) before the final mixture is blown into a cold corebox 41. The latter can be located on a table 42 which is movable up and down to effect clamping and release of the corebox 41; or the table can remain stationary and the blowing chamber 40 can be movable up and down instead. And, as the machine is designed for flow-production, provision has to be made for automatically feeding it with a succession of coreboxes. They can be indexed as a line feed beneath the blowing chamber 40, or a rotary table carrying several coreboxes can be indexed circumferentially.

Another feature which has not yet been mentioned is that the final mixer 27 is fitted with airblast jets which, at the appropriate stage of the operating cycle of the machine, are automatically turned on in order to clean the final mixer. One of these jets is indicated at 43 (FIG. 1) on the central guide 20A.

The operating cycle of the machine will now be described, starting from the point where the two segregated mixes (which were prepared during the previous cycle) are in their respective hoppers 17 and 18. From this point the operations are as follows:

a. The corebox 41 is clamped.

b. The two screw-type mixers S and 6 are started and run for a set period of time, depending upon the actual chemical system involved.

c. The resin and hardener pumps 9 and 12 are started and run for a set period of time, depending upon the actual chemical system involved.

d. The final mixer 27 is started.

e. The valve 19 between the two hoppers 17 and 18 and the final mixer 27 is opened and then closed again.

f. The sand hopper outlet valves 2 are opened, and are closed again when the resin and hardener pumps 9 and 12 and the screw-type mixers 5 and 6 are stopped.

The final mixing takes place for a set period of time. fiOperations (a) to (f) are all initiated simultaneously).

h. The outlet valve 30 of the final mixer 27 is opened, and the airblastjets 43 are operated to clean this mixer.

i. the outlet valve 30 is closed, as well as the inlet valve 36 of the blowing chamber 40.

j. The final mixer 27 is stopped.

(Operations (i) and (j) take place simultaneously).

k. The airblast of the blowing chamber 40 is turned on for approximately 2 seconds.

l. The inlet valve 36 of the blowing chamber 40 is opened.

m. The corebox 41 is unclamped. (Operations (l) and (m) take place simultaneously).

The final stage of the operating cycle is that the core is allowed to harden sufficiently for it to be removed from the corebox.

We claim:

1. A cold-box core-making machine for producing resinbonded foundry cores, comprising, in combination, a hopper containing sand of which the temperature and moisture content are controlled, the sand hopper having two timer-controlled outlet valves; two separate mixing devices to which controlled amounts of sand can be delivered from the respective hopper outlets; means for supplying resin to one of the mixing devices; means for supplying hardener to the other mixing device; two separate hoppers into which the segregated mixes are delivered; a final mixer for producing a homogeneous mixture of all the materials; timer-controlled outlet valve means by which the respective mixes are delivered to the final mixer; a blowing chamber in communication with the final mixer and serving a cold corebox; timer-controlled valve means for dispensing the final mix into the blowing chamber; and a timer-controlled valve effective to obturate communication between the final mixer and the blowing chamber before the final mixture is blown into the corebox.

2. A cold-box core-making machine according to claim 1, in which the outlet valves of the sand hopper are of the slidableplate type, and the controlling edge of each of these valves incorporates a V-shaped notch which affords a variable area aperture as it is moved across the corresponding outlet.

3. A cold-box core-making machine according to claim 1, in which the timer-controlled outlet valve means by which the respective mixes are delivered to the final mixer comprises a pair of rigidly interconnected slide-valves each controlling a bottom outlet of the corresponding one of the two separate hoppers. 

1. A cold-box core-making machine for producing resin-bonded foundry cores, comprising, in combination, a hopper containing sand of which the temperature and moisture content are controlled, the sand hopper having two timer-controlled outlet valves; two separate mixing devices to which controlled amounts of sand can be delivered from the respective hopper outlets; means for supplying resin to one of the mixing devices; means for supplying hardener to the other mixing device; two separate hoppers into which the segregated mixes are delivered; a final mixer for producing a homogeneous mixture of all the materials; timer-controlled outlet valve means by which the respective mixes are delivered to the final mixer; a blowing chamber in communication with the final mixer and serving a cold corebox; timer-controlled valve means for dispensing the final mix into the blowing chamber; and a timer-controlled valve effective to obturate communication between the final mixer and the blowing chamber before the final mixture is blown into the corebox.
 2. A cold-box core-making machine according to claim 1, in which the outlet valves of the sand hopper are of the slidable-plate type, and the controlling edge of each of these valves incorporates a V-shaped notch which affords a variable area aperture as it is moved across the corresponding outlet.
 3. A cold-box core-making machine according to claim 1, in which the timer-controlled outlet valve means by which the respective mixes are delivered to the final mixer comprises a pair of rigidly interconnected slide-valves each controlling a bottom outlet of the corresponding one of the two separate hoppers. 